KEY STAR TECHNOLOGIES: DISPERSED MULTIPHASE FLOW AND LIQUID FILM - PowerPoint PPT Presentation

KEY STAR TECHNOLOGIES: DISPERSED MULTIPHASE FLOW AND LIQUID FILM MODELLING DAVID GOSMAN EXEC VP TECHNOLOGY, CD-adapco

INTRODUCTION KEY METHODOLOGIES AVAILABLE IN STAR-CCM+ AND STAR-CD 1. Lagrangian modelling of dispersed multiphase flow of droplets or solid particles. 2. Modelling of droplet or solid particle impact on walls. 3. Modelling of liquid film formation, dynamics, heat/mass transfer  in all cases with full interaction with continuous phase. • STAR -CCM+ generally applicable (e.g. aeronautical, chemical process, oil/gas, medical, etc) • STAR -CD specifically targeted at reciprocating internal combustion engine (ICE) modelling

INDUSTRIAL APPLICATIONS Aerospace Automotive Chemical Process Energy Oil and Gas Manufacturing Process … and many more

ATOMISATION MODELLING - OVERVIEW • modelling of droplet formation by breakup of liquid stream • provides initial conditions for Lagrangian spray simulation • built -in models for several atomiser types • may also include internal flow in atomiser Pressure swirl atomiser Pressure jet atomiser

ATOMISATION MODELLING – OPTIONS AVAILABLE range of approaches available in both STAR-CCM+ and STAR-CD: - empirical, including user input - phenomenological/experiment-based - physics-based, transport equations Liquid core nozzle AVAILABLE MODELS STAR- STA Typical CCM+ R-CD Application surface User input – individual droplets ✓ ✓ general ✓ ✓ - distribution ✓ Huh model (pressure jet) ICE ✓ ✓ Reitz-Diwaker (pressure jet) ICE ✓ MPI model (pressure jet) ICE ✓ LISA model (conical spray) gas turbine ✓ ELSA model (nozzle flow and/or atomisation) ICE, general ✓ ✓ LES/VOF (high-resolution nozzle flow and/or general atomisation)

ATOMISATION MODELLING - EXAMPLES Simulation of spray atomisation by pressure jet nozzle with STAR-CCM+ Includes flow within nozzle High-resolution VOF/LES, including cavitation

ATOMISATION MODELLING - EXAMPLES Simulation of spray atomisation by pressure jet nozzle with STAR-CCM+ High-resolution VOF/LES, including internal nozzle flow and cavitation

LAGRANGIAN DISPERSED FLOW MODELLING – OVERVIEW multiphase modelling of dynamics, heating, evaporation/condensation of droplets or solid particles. solve Lagrangian conservation equations for statistically representative particles, along with Eulerian conservation equations for fluid phase phase equations fully-coupled

LAGRANGIAN MODELLING – SOME DETAILS Particle and continuum fluid conservation equations Particle momentum Particle location d x d Particle mass dt = u d Particle energ y Fluid momentum particles

LAGRANGIAN MODELLING – SOME DETAILS built-in models in STAR-CCM+/STAR-CD for key phenomena, including - droplet turbulent dispersion, breakup, collision and coalescence - interphase heat/mass transfer disperse - chemical reaction (coal combustion) FEATURES MODELLED STAR- STAR CCM+ -CD Particle material – fluid ✓ ✓ ✓ - solid breakup ✓ ✓ Interphase Drag ✓ ✓ Turbulent dispersion ✓ ✓ Breakup ✓ ✓ Droplet collision, coalescence collide/coalesce Interphase heat transfer – sensible ✓ ✓ ✓ ✓ - latent ✓ - radiative Multicomponent mass transfer – miscible ✓ ✓ ✓ - immiscible ✓ ✓ Boiling, critical point thermodynamics ✓ Electrostatic forces disperse ✓ Particle combustion (coal)

LAGRANGIAN MODELLING – VALIDATION EXAMPLE Evaporating Diesel spray simulation P inj = 1300 Bar 0,060 0,025 liquid penetration (m) 0,050 0,020 vapor penetration (m) 0,040 0,015 0,030 calculation (90%) 0,010 calculation (0.1%) 0,020 EXP 0,005 0,010 EXP 0,000 0,000 0,0000 0,0005 0,0010 0,0015 0,0000 0,0005 0,0010 0,0015 t(s) t(s) liquid penetration vapour penetration

WALL IMPACT MODELLING - OVERVIEW prediction of regimes and outcomes of droplet or solid particle impact on wall. regime can depend on: droplet dynamics; surface temperature, roughness, material…… outcome can include deposition, secondary breakup……. solid particle impact can lead to wall erosion

WALL IMPACT MODELLING – SOME DETAILS Models available in both STAR-CCM+ (droplets, solid particles) and STAR-CD (droplets) Strongly experiment-based Regimes and outcomes for droplets:

WALL IMPACT MODELLING - OPTIONS Models for droplet and/or solid particle impact in STAR-CCM+ and STAR-CD FEATURE MODELLED STAR- STAR CCM+ -CD particle material – fluid ✓ ✓ ✓ - solid droplet impact regime identification ✓ ✓ - dry, wet wall ✓ ✓ - user specified droplet impact outcome ✓ ✓ - secondary droplet size, velocity ✓ ✓ - liquid deposition rate ✓ droplet-wall heat transfer ✓ droplet multicomponent evaporation- finite rate ✓ - instantaneous ✓ user-specified particle stick/rebound/escape ✓ wall erosion rate ✓ Ice accretion rate

WALL IMPACT MODELLING – VALIDATION EXAMPLE Simulation of spray impingement on cold wall using STAR-CD 2.6ms 4.6ms 6.6ms 8.6ms measured calculated

LIQUID FILM MODELLING - OVERVIEW prediction of dynamics, heat/mass transfer, melting/solidification of thin liquid film on wall film may be result of spray impact, condensation, melting, inlet boundary…….. interaction with adjacent fluid phase via interface boundary conditions and special deposition and stripping models. modelled by solving Eulerian conservation equations in special way, avoiding need for fine mesh across film.

LIQUID FILM MODELLING – SOME DETAILS • assume film thin, laminar, locally smooth • express Eulerian conservation equations in integral form across film thickness δ in wall-normal direction n, δ n φ • assume normalised wall-tangential velocities and temperature, concentrations vary quadratically across film • result is two-dimensional conservation equations for film thickness δ , mean velocity u mean ; temperature T mean etc as functions of wall-tangential coordinates and time. • solve 2D equations by finite -volume method – fast, efficient, can accommodate arbitrarily thin films.

LIQUID FILM MODELLING – SOME DETAILS Modelling options in STAR-CCM+ and STAR-CD Features Modelled STAR STAR - -CD CCM+ ✓ ✓ Transition from isolated droplet deposition to film interphase momentum transfer via ✓ ✓ - interfacial drag ✓ ✓ - interfacial deposition/stripping internal and interphase energy transfer ✓ ✓ - conduction/convection/boiling ✓ ✓ - evaporation/condensation ✓ ✓ - deposition/stripping internal and interphase mass transfer ✓ ✓ - multicomponent ✓ ✓ - evaporation/condensation ✓ ✓ - deposition/stripping ✓ ✓ stripping removal ✓ ✓ edge separation removal ✓ solid particle ingestion ✓ solidification/melting

LIQUID FILM MODELLING – VALIDATION EXAMPLES Simulation of air blast atomisation using STAR-CCM+ Liquid film, stripping, Lagrangian droplets Coarse Grid Resolution

OIL/GAS APPLICATION – PIPELINE EROSION Simulation of undersea pipeline erosion using STAR-CCM+ Multiphase oil-water-sand mixture Lagrangian solid particle, erosion models

AUTOMOBILE APPLICATION – RAIN MANAGEMENT Simulation of rain impact on automobile exterior Lagrangian droplets, liquid film, stripping

AUTOMOBILE APPLICATION – CATALYTIC CONVERTOR Simulation of urea injection in automotive catalytic convertor Lagrangian spray, liquid film, boiling

MANUFACTURING APPLICATION – SPRAY PAINTING Simulation of automobile spray painting process with STAR-CCM+ Lagrangian spray, overset mesh

MEDICAL APPLICATION – METERED DOSE INHALER Simulation of metered dose inhaler operation with STAR-CCM+ Lagrangian spray, liquid film, evaporation

AEROSPACE APPLICATION – WING ICING Simulation of aircraft wing icing with STAR-CCM+ Lagrangian spray, liquid film, freezing/melting

AEROSPACE APPLICATION – ENGINE NACELLE ICING Simulation of aircraft engine icing with STAR-CCM+ Lagrangian spray, liquid film, freezing/melting, mesh morphing

SUMMARY Powerful, unique methodologies in STAR-CCM+ for simulating dispersed multiphase and liquid film flows, separately or in combination Extensive and continuing validation and refinement Many industrial applications already – but potential for much more Further extensions envisaged